Ancient Man`s Genetic Code Copied In Laboratory Setting

May 28, 1985|By Harold M. Schmeck Jr., The New York Times

NEW YORK — Human genetic material, largely undamaged after 2,400 years, has been extracted from an Egyptian mummy and has been grown in the laboratory. The achievement is the most dramatic of a series of recent accomplishments using molecular biology to study links between modern and ancient life.

Details of the recovery of DNA from the mummy were recently published in the scientific journal Nature. The achievement, by Dr. Svante Paabo of University of Uppsala in Sweden, is believed to be the first in which DNA, the genetic material in all forms of life, has been resurrected and duplicated from an ancient human or from any other specimen of such antiquity.

The ability to reproduce DNA from such an ancient source is expected to be a powerful new aid to archaeology and to the study of evolution.

Paabo said the new findings show it is feasible to study DNA from ancient sources. In the future, the Swedish scientist hopes to find genetic material from viruses in mummy tissues. If successful, this would be a great aid to the study of the evolution of viruses in the human population.

Scientists of University of California at Berkeley recently detected DNA in a sample of muscle from a mammoth that died 40,000 years ago.

Last year the same group extracted and reproduced DNA from an African mammal called a quagga that became extinct a century ago. It was a relative of the zebra and the horse. Reproduction of fragments of its genetic material represented the first time such a biochemical resurrection had ever been achieved with the DNA of any extinct animal.

Dr. Allan M. Wilson, leader of the research group in Berkeley, said the new work in Uppsala was ``a notable achievement.``

Today study of evolution is moving more and more into the realm of molecular biology and chemical analyses done in the laboratory.

The successful cloning of genetic material from a mummy is the most spectacular achievement of this kind to date. Even before this, however, the results of biochemical studies of evolution have often been surprising, as well as important. Specialists see reason to hope for even more important developments in the future.

Wilson, for example, believes the new uses of molecular biology may be valuable in attacking the puzzle of Neanderthal man`s relationship to modern humans. The most important consequence of research in this field so far has been in the study of human evolution.

The fossil evidence, collected carefully over many years, had led scientists to believe the evolutionary line that led to humans diverged from that of the apes more than 25 million years ago. But comparison of blood substances from humans and chimpanzees indicates the divergence was much more recent, perhaps no more than 5 million to 7 million years ago.

In the early 1970s, many paleontologists considered this more recent date to be rank heresy. But, over the years, much more evidence has been found, including persuasive data from analyses of DNA, the master chemical of heredity.

Changes in a mammalian species` DNA that occur over time can be used as an evolutionary clock, Wilson said. The DNA from cell nuclei changes at the rate of about 0.4 percent each million years.

The DNA from important intracellular structures called mitochondria evolves much more rapidly; at a rate approaching 2 percent every million years. Mitochondrial DNA is much studied today, partly because of its more rapid evolution.

Dr. C.G. Sibley and Dr. J.E. Ahlquist of Yale, who have made major contributions to the DNA clock idea, have estimated the human-ape divergence at about 7 million years.

Detection of DNA in a specimen of muscle from the mammoth was achieved by Dr. Russell Higuchi, chief molecular biologist of the Berkeley laboratory. The tissue came from a calf of that extinct species that must have died 40,000 years ago.

Higuchi is now trying to grow pieces of the 40,000-year-old mammoth DNA in bacteria, a process called gene, or molecular, cloning.

If successful it would produce enough of the scarce DNA for extensive studies. In a limited sense it would also be a feat close to bringing that long quiescent genetic material back to life, since it would be reproducing in the bacterial cells as they grew and multiplied.

The fact that DNA in detectable amounts has survived for 40,000 years has given the scientists hope that genetic material of other long vanished species may be found and studied usefully in the laboratory.

Further support for that hope has come from the achievement by Paabo and his colleagues in Sweden. While they have recovered only small fragments of DNA from the mummified tissue, much can be learned from such material.

The scientists at Berkeley have been pursuing the ancient traces of life in the form of DNA in several species including an extinct relative of the bison, called the steppe bison, that was also preserved in a frozen state since the last ice age and was uncovered several years ago in Alaska.